Method of sealing a sump

ABSTRACT

A method of lining a sump includes applying an elastomeric material to a surface of the sump by spraying the elastomeric material onto a surface of the sump whereby a continuous elastomeric coating is formed on the surface. An effective spray-on polymer is a polyurethane polymer. The sump walls may be partially or wholly coated.

This invention relates to underground piping systems, and specifically to a method for lining and sealing a sump that is mounted on an underground, liquid storage tank.

BACKGROUND

Sumps are widely used in the field of secondary containment for the underground transfer of hazardous fluids including gasoline and diesel fuels. Sumps are prefabricated chambers that are commonly placed on top of a fluid storage tank and beneath a manhole cover in a gas station. The sumps allow access to the piping equipment. In a pressure system, the sump typically houses a portion of a pump and its associated piping fittings. In a suction system, the sump does not house a pump, but it will typically include fuel piping. The sump generally has through-wall openings to permit the passage of pipes going into the tank and through the side wall of the sump. These openings may have gaskets or bulkhead fittings to form a fluid tight seal about the pipe and to prevent ground water from leaking into the sump. In addition to keeping ground water out of the sump chamber, the sump is intended to prevent the escape of a leaked, hazardous fluid into the environmental soil.

Many sumps may develop leaks as a result of improper installation, degradation of seals, ground water hydrostatic pressure, or other reasons. Typically, leaky sumps must be repaired by excavation techniques that are necessary to completely replace a sump or at least replace a portion thereof. This type of repair is extremely time consuming and expensive.

Another type of repair of sumps is described in U.S. Pat. No. 5,870,871. In the repair method described therein, a plurality of film pieces are placed inside the sump to create a liner substantially conforming to the interior dimensions of the sump. The pieces are joined together to form a unitary containment shell. A problem with this method is the difficulty with proper installation of the pieces of liner.

SUMMARY

Accordingly it is an object of the present invention to overcome the foregoing problems and provide a liner for a sump. The liner is a coating of elastomeric material that is sprayed onto the surface of the sump to create a durable and fluid tight seal.

In one embodiment, a method of lining a sump comprises applying elastomeric material to a surface of the sump by spraying the elastomeric material onto a surface of the sump whereby a continuous elastomeric coating is formed on the surface. The elastomeric coating is then allowed to cure whereby an elastomeric liner is formed on the surface to seal the sump. The surface of the sump may be pre-treated by mechanical roughing of the surface of the sump prior to the coating step. Also, the surface of the sump may be pre-treated by heating of the surface of the sump. The heating and mechanical roughing steps may both be used to pre-treat the surface of the sump, and the heating step may take place before the step of roughing of the surface. The elastomeric material may be a polyurethane polymer, and it may be coated to a thickness of from about ⅛ of an inch to about ¼ of an inch. The spraying step may comprise spraying the elastomeric material over substantially the entire interior surface of the sump or, alternatively, over a portion of or the entire exterior surface of the sump.

In another example, an assembly includes a sump and a coating, the assembly comprising a sump having side walls and forming part of an underground piping system. The sump comprises an opening in one sidewall for permitting passage of a pipe. The assembly includes a sprayed-on elastomeric coating on at least the one sidewall comprising an opening therein, wherein the elastomeric coating forms a seal around the opening to create a fluid tight chamber within the sump. The sump may comprise a plurality of openings adapted to permit passage of a plurality of pipes. The elastomeric coating may cover substantially the entire inside of the sidewalls of the sump. The thickness of the coating may be from about ⅛ of an inch to about ¼ of an inch. The elastomeric coating may be a polyurethane polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation, cross sectional view of a sump mounted onto a fluid tank as shown in an underground environment.

FIG. 2 is a side elevation view of the sump as shown in FIG. 1, further displaying an elastomeric coating on the surface of the sump.

FIG. 3 is a side elevation view of the sump shown in FIG. 1, further displaying an elastomeric coating over the entire surface of the inside of the sump.

FIG. 4 is a perspective, cut away view of a sump showing a pipe extending through the sidewall of the sump.

FIG. 5 is a perspective view of the sump shown in FIG. 4 wherein the inside surface of the sump around the pipe has been sprayed with an elastomeric coating.

Detailed Description

FIGS. 1-5 illustrate various alterative examples of a prior art sump (FIG. 1) and a sealed sump as described herein (FIGS. 2-5). The focus of each example is the use of a sprayed-on elastomeric material to seal or reenforce the sump, thereby enhancing its fluid tight capabilities.

FIG. 1 shows a sump 10 that is mounted on the wall 12 of an underground storage tank 13. The sump 10 is buried in dirt or gravel 14. In a traditional gas station setting, the sump 10 is mounted underneath pavement or concrete 16. Access to the sump 10 is available through a manhole cover 18 that is mounted onto a manhole ring 20 that is fixed in the pavement or concrete 16.

The sump 10 is typically made up of fiberglass or plastic and includes a sidewall 25 that defines a chamber 27 therein. The sump 10 has an opening 31 that is covered by a lid 30 that is in a sealing engagement with the sump opening 31. The sidewall 25 of the sump 10 includes an opening 35 in which is mounted a fitting 36 and pipe 37 that passes through the sidewall 25. The fitting 36 is of a material and fit appropriate to create a seal of the opening 35 in the sidewall 25. Inside the sump chamber 27, there is shown a pump 42 that includes a pipe 40 and pipe fitting 41 that feed down into a fluid storage tank 13 through sidewall 25 and the fluid storage tank wall 12.

The foregoing description of a sump installation is a typical construction. As noted earlier, however, the fittings 36 and 41 may deteriorate over time or they may have been improperly installed to allow liquid seepage into an out of the chamber 27 of the sump 10. Still further, the sidewalls 25 of the sump 10 may deteriorate over time or have been damaged during installation or maintenance so that cracks or other weak points develop that may likewise be a source of seepage of fluid into or out of the chamber 27.

FIG. 2 illustrates a sump 10 that is essentially the same as the sump shown in FIG. 1 except that there are areas where a polymer has been coated onto the surface of the sidewalls 25 to form a continuous elastomeric coating hereon. As shown in FIG. 2, a spray-on elastomeric material is shown on the inside surface 50 and the outside surface 51 around the opening 35 where the pipe 37 passes through the sidewall 25. Also, the spray-on polymer 52 is shown being coated around the fitting 41 where the pipe 40 passes through the sidewall 25 in connecting the fluid storage tank 13 to the sump 10. As shown in FIG. 2, the spray-on coating is on the inside 50 and outside 51 surfaces of the sump sidewalls 25 around the opening 35. Of course, the coating may be effectively used on just the outside 51 or just the inside 50. Such a coating would also be effective if there was another known leakage point in the sump, for instance where a wall was damaged during installation or maintenance. Specific weak spots may be coated with a spray-on polymer to further ensure the fluid tight attribute of the sump 10.

In FIG. 3, the entire inside surface of the sidewalls 25 of the sump 10 is coated with elastomeric material 55. Such a full surface treatment may be used upon installation of a sump in a particularly wet site. In this way, the owner of the tank and sump 10 do not need to wait for a leakage problem to occur. The owner could simply coat the entire inside surface as shown. Another alternative is that all of or a part of the outside of the sidewalls 25 may be coated when the sump is installed and before the dirt or gravel is filled in around the sump 10. FIG. 2 and the coating 51 is an example of a partial coating on the outside of the sump sidewall 25.

FIGS. 4 and 5 illustrate a sump 110 having sidewalls 120 and pipe 130 extending through the sidewalls 120 through fitting 131. The shaded area 140 around the pipe 130 is a portion of the sump that may be treated with a spray on polymer to prevent any potential leakage. It is preferred that the sidewall 120 be prepared prior to spraying on the elastomeric material. The first step is to thoroughly clean the surface where the polymer will be applied, preferably using isopropyl alcohol or other cleaning solvent. The surface should be wiped clean and dried. Also, the shaded area 140 may be heated with a torch. Alternatively, the area may be mechanically roughened with a grinding stone. Still further alternatively, the area 140 may be heated and mechanically roughened prior to the spraying on of a polymer 145. While it is envisioned that the site where the spray-on polymer will be used will be pretreated, such preparation is not absolutely necessary depending on the type and condition of the sump sidewall material where the particular spray-on polymer that may be used. The preparation through heating and mechanical roughing has simply been discovered to be effective in the creating of a tight seal.

In FIG. 5, the elastomeric material 145 is shown as it has been applied around the pipe 130 extending through the sidewalls 120. As demonstrated in FIG. 3, this polymer coating may alternatively cover the entire inside surface of the sidewalls 120 of the sump 110. Such an application is at the discretion of an installer and/or sealer. Given site conditions may make such a comprehensive coating an effective preventive step.

A number on spray-on polymers (also referred to throughout as elastomeric materials) may be effective for the purpose of sealing a sump as described herein. A common type of spray-on polymer application is currently a truck bed-liner application. One particular type of spray-on polymer, NSF-100 (Speciality Products, Inc.), has been found to be effective in the present sump examples. The application process that is followed is as instructed by published Specialty Products' application procedures. But in any event, it is no different than the spray-on polymer process for a truck bed liner. In one example, the polymer is sprayed on to a thickness of about ⅛ inch to about ¼ inch. Other spray-on polymers will be effective and acceptable depending on the type of fluid that may be handled through the sump. The NSF-100 product is a polyurethane polymer. Other elatomeric polymers such as polyureas may be used. Other polymers may be found to have effective properties with respect to sealing and longevity.

Once the elastomeric material is sprayed onto the desired surface of a sump, it is allowed to cure to form the continuous elastomeric coating. From an installation convenience perspective, it is desirable to spray on a relatively fast-curing polymer mixture like, for instance, the NSF-100 polyurethane identified herein.

The elastomeric material discussed herein is prepared by reacting an isocyanate-terminated compound or polymer containing at least two reactive isocyanate groups with an amine compound or polymer containing at least two reactive amine groups. The two reactive components are mixed immediately before being spray applied to the surface to be coated. Because of the very reactive compounds used and the fast-curing nature of the elastomeric material formed from the reactive components, the reactive components are preferably mixed directly in a spray gun. Suitable spray guns are commercially available.

EXAMPLE

A standard polyethylene sump wall material was used to create a pressure test. The polyethylene wall was tested for strength alone, without any pipe joint or spray-on polymer. This was then compared with the same polyethylene sump wall material having a pipe joint and a spray-on polymer. In preparing the sample that included the joint and the spray-on polymer, the area around the opening was heated with a torch for approximately a minute and then roughened all around the opening. The spray-on polymer (NFS-100) was then applied using conventional application equipment to a thickness of about ⅛ inch to about ¼ inch. The sump sidewall without any spray-on polymer or pipe joint was found to have a rupture pressure of 110 psi. The sump sidewall material that included a pipe fitting and a spray-on polymer coating had a rupture pressure of 120 psi. In other words, the combination of the coating with the opening in the sidewall material was stronger than the sidewall material alone without any openings. The coated joint was stronger than the sidewall itself.

It should be noted that the examples herein refer to the repair of a tank sump in a pressure system, i.e., a sump housing a pump and mounted on top of an underground storage tank. The method described herein can be readily used to repair: (i) tank sumps used in suction systems; (ii) junction sumps used in either pressure or suction systems; or (iii) dispenser sumps used in either pressure or suction systems.

While the invention has been described with reference to specific embodiments thereof, it will be understood that numerous variations, modifications and additional embodiments are possible, and all such variations, modifications, and embodiments are to be regarded as being within the spirit and scope of the invention. 

1. A method of lining a plastic sump comprising the steps of: re-treating a surface of the plastic sump; applying an elastomeric material to the pre-treated a surface of the sump by spraying the elastomeric material onto the a surface of the sump wherein a continuous elastomeric coating is formed on the surface; and allowing the elastomeric coating to cure, whereby an elastomeric liner is formed on the surface to seal the sump.
 2. A method of lining a sump as described in claim 1, wherein the pre-treating step comprises mechanical roughing of the surface.
 3. A method of lining a sump as described in claim 1, wherein the pre-treating step comprises heating of the surface.
 4. A method of lining a sump as described in claim 2, wherein the pre-treating step further comprises heating of the surface.
 5. A method of lining a sump as described in claim 4, wherein the step of heating the surface precedes the step of roughing of the surface.
 6. A method of lining a sump as described in claim 1, wherein the elastomeric material is a polyurethane polymer.
 7. A method of lining a sump as described in claim 1, wherein the resulting elastomeric coating has a thickness of from about ⅛ inch to about ¼ inch.
 8. A method of lining a sump as described in claim 1, wherein the spraying step comprises spraying the elastomeric material over substantially the entire interior surface of the sump.
 9. A method of lining a sump as described in claim 1, wherein the spraying step comprises spraying the elastomeric material over substantially the entire exterior surface of the sump.
 10. An assembly including a plastic sump and a coating, the assembly comprising: a plastic sump having sidewalls and forming part of an underground piping system and comprising an opening in the sidewall for permitting passage of a pipe; a sprayed-on elastomeric coating on at least a portion of the sidewall comprising an opening therein; wherein the elastomeric coating forms a seal around the opening to create a fluid tight chamber within the sump.
 11. An assembly as described in claim 10, wherein the sump comprises a plurality of openings adapted to permit passage of a plurality of pipes.
 12. An assembly as described in claim 10, wherein the elastomeric coating covers substantially the entire inside surface of the sidewalls of the sump.
 13. An assembly as described in claim 10, wherein the thickness of the coating is from about ⅛ inch to about ¼ inch.
 14. An assembly as described in claim 10, wherein the elastomeric coating is a polyurethane polymer. 